There are many traffic lights in a city. When a vehicle run into a red light, it must stop and wait until the light changes to green before it is allowed to go. Stopping wastes energy on fuel and causes more pollution. It wastes travel time also. That is why the hybrid vehicles are hot now, but hybrid vehicles are expensive. Hybrid vehicles lose energy in both conversion of kinetic energy to chemical energy and conversion of chemical energy to kinetic energy. Hybrid vehicles can not convert kinetic energy to chemical if the battery is fully charged. Hybrid vehicles do not save time.